Lambda 8300 ROM disassembly

[stefano]

I'm proud to annonunce I was able to compare the commented ZX81 ROM assembly listing and the Lambda ROM disassembly and to comment a good portion of it.

It is an amazing piece of code, a considerable effort was made to obfuscate the binary fingerprint of the derived ROM, but also several improvements were inserted.

I was impressed by the many smart tricks applied to save code space, I thing that it can be an interesting peek for all the surviving assembly programmers in this list !!

EDIT: 2015/07/31 - updated (BASIC tokens and keyboard codes decoded + improvements and fixes).

EDIT: 2015/08/03 - furtherly updated (sound code, interpreter engine and display driver).

EDIT: 2015/08/11 - more fixes and updates

[stefano]

Last minute correction: please be aware that the comments aside the FP-CALCULATOR opcode tables need a little fix: the opcodes related to the "true binary operations" must be updated with a progressive HEX code.

EDIT: corrections are now applied to the updated file.

[sascha2000]

Hello,

very good work. Thank you for the same.

I think the Lambda is such a nice clone, it is worth to work with it.

I have installed the ZX81 compatible ROM on it, except hires graphics, it runs text mode apps very well.

https://www.youtube.com/watch?v=lH8igenBmuY

Regards
Sascha

[stefano]

Thankyou,
I used it as a cross-reference to prepare the z88dk support, now at an half-working stage.
A lot of the experience coming from the ZX81 work can be reused !
I have prepared a compiled prototype (in attachment) and I'd like to know if it works.
The game barely runs because of the lack of a complete text driver (the display does not scroll and some character should be mapped differently), but it can be played.

I need to know whether the picture is stable on the real hardware (PAL and NTSC) and if the WAV format is valid for the LAMBDA. Can anybody help ?

[stefano]

The new Lambda 8300 target port is almost ready in the z88dk CVS tree. Hopefully the first nightly compiled release will be available tomorrow morning

[stefano]

Ok.. actually something went wrong, let's hope for tomorrow :S

[stefano]

First nightly releases are coming out.
Whatch out ! A couple of bugs are still creeping in but most of the zx81 functionalities are already present and working: (SLOW mode support, blocky graphics, CHROMA81-style APIs, interfacing to BASIC program and variables, ultra compact ROM based Floating Point library but a faster z88dk provided option available..)

[sascha2000]

Hello Stefano,

sorry I was ill and so I did not read your thread.

>I have prepared a compiled prototype (in attachment) and I'd like to know if it works.

I will try to run it on my lambda. This may take some days .... please be patient ...

[stefano]

Please don't apologise !!
I appreciate any kind of feedback, the past experiences taught me not to fully trust the emulators

[stefano]

Forgot to say that there is a couple of entries in the "games" section you might prefer